The overall objective of the proposed research is a better understanding of the biochemical and hormonal control mechanisms by which mammalian adipocytes regulate the rate of glucose uptake and conversion into its major metabolic products, CO2, glyceride-glycerol and glyceride-fatty acids. The studies will be conducted with isolated adipose cells, varying in mean diameter and volume, removed from subjects of different species with varying degrees of adiposity. Investigations will include the following objectives: 1) Definition of the role played by fat cell size in the rate and pattern of glucose metabolism and cellular response to insulin and lipolytic hormones; 2) Clarification of the influence of lipolysis and lipolytic products in particular fatty acids accumulation within the fat cell, on the rate of glyceride synthesis from glucose and on the insulin effect on rate and pattern of glucose utilization; 3) Study of the mechanisms by which insulin and epinephrine stimulate hexose transport by small and larger adipocytes; 4) Characterization of the effects of age and nutritional state of the subjects on the fat cell size, metabolic activity and hormonal responsiveness. Techniques to study simultaneously a multiplicity of metabolic parameters and their interrelationships in cell samples of well- characterized isolated adipocyte populations have been developed. The metabolic activities will be expressed on the basis of fat cell number and as functions of the cells' diameter, surface area or volume.